I have almost 80GB of music on my iPod, and I love everything that's on there. In fact, I don't put music on there that even has a chance of me not liking it. Couple things to note, I have the Rockbox firmware on my iPod, so most of my music is in FLAC. The ones that aren't in FLAC, are my absolute favorites, and they are in AIFF or WAV.
And yes, you can hear the difference with $400 Shure in ears, or even on my studio monitors.
I have less than a GB of other stuff on my iPod, and only 5GB are free. I also own everything that's on there. If that's not someone that loves music, I don't know what is.